Web slitting apparatus

ABSTRACT

Apparatus for slitting a web of paper longitudinally consists of a slitting knife, mounted on a carrier member above the web, and a counter member, against which the knife cuts, on carrier member below the web which is f ed between the carrier members during the slitting operation. To enable the position of the knife and counter-member to be changed so as to slit the web in a different position the confronting faces of the two carrier members are provided with rollers, or belts, and the carrier members are provided with rollers, or belts, and the carrier members are urged towards each other, so that the rollers, or belts interengage. When one of the carrier members is moved horizontally across the path of the web, the interengagement of the rollers or belts causes the other carrier member to move also and the two carrier members will remain in the same relative positions.

United States Patent 1 91 Langworthy et al.

[451 Sept. 25, 1973 WEB SLITTING APPARATUS [75] Inventors: Colin George Langworthy; Edwin James Webb, both of Bristol, England [73] Assignee: Masson Scott Thrissell Engineering Limited, London, England [22 Filed: Apr. 21, 1971 [21] Appl. No.: 135,833

[30] Foreign Application Priority Data Apr. 23, 1970 Great Britain 19,595/70 [52] US. Cl 83/482, 83/428, 83/498 [51] Int. Cl. B26d 1/22, B26d 5/02 [58] Field of Search 83/499, 498, 428,

[56] References Cited UNITED STATES PATENTS 3,511,124 5/1970 Bruns 83/925 CC 3,367,225 2/1968 Stanford et al. 83/499 3,540,340 11/1970 Koskela 83/499 Primary Examiner-Frank T. Yost Attorney-Craig, Antonelli & Hill ABSTRACT Apparatus for slitting a web of paper longitudinally consists of a slitting knife, mounted on a carrier member above the web, and a counter member, against which the knife cuts, on carrier member below the web which is f ed between the carrier members during the slitting operation, To enable the position of the knife and counter-member to be changed so as to slit the web in a different position the confronting faces of the two carrier members are provided with rollers, or belts, and the carrier members are provided with rollers, or belts, and the carrier members are urged towards each other, so that the rollers, or belts interengage. When one of the carrier members is moved horizontally across the path of the web, the interengagement of the rollers or belts causes the other carrier member to move also and the two carrier members will remain in the same relative positions.

14 Claims, 6 Drawing Figures qzazw PATENTEDSEPZSIHB 3,760,675

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INVENTORS COLIN GEORGE LANGWORT'HY and EDWIN JAMES WEBB Cmu'8 MM 1 Mill ATTORNEYS PATENTEUSEPZSIQYS sum 2 OF 3 INVENTORS COLIN EORGE LANGWORTHY m: EDWIN xmes WEBB ATTORNEYS PATENTED 8EP25I975 SHEET 3 0F 3 INVENTORS g COLIN GEORGE LANGWORTHY L ma EDWIN IAMESWEBB r g, o

ATTORNEYS WEB SLITTING APPARATUS This invention relates to apparatus for slitting webs of paper or the like longitudinally. Usually this type of apparatus consists of pairs of cutting elements each comprising a circular slitting knife engaging one face of the web and a counter-member engaging the opposite face of the web so as to coact with said knife. Such apparatus produces a plurality of narrow webs from a single wide web, and is frequently used in association with a cross-cutting apparatus which cuts the narrow webs transversely to produce sheets.

It is common to provide for adjustment of the pairs of slitting knives across the width of the web so as to vary the number and widths of narrow webs produced. Various devices have been proposed for carrying out this adjustment, usually by providing a connection between carriers on which each knife and its associated counter-member are mounted,'so that each such pair of cutting elements can be moved in unison whenever their slitting position is changed. One element of each pair is normally movable out of engagement with the other while such a change of position is taking place.

A disadvantage of this type of apparatus is that the connection between the carriers, although only engaged while a change of position is taking place, fouls the web as the carriers are moved across it to their new slitting position.

In other forms of apparatus it has been proposed to move the two elements of each pair separately, but this increases the time required to effect re-positioning of the cutting elements sufficiently to cause a material reduction in the total output of the slitting apparatus.

It is an object of the present invention to provide an improved carrier forthe cutting elements of web slitting apparatus, with which changes of the positions of the cutting elements are facilitated.

According to the invention there is provided a carrier for cutting elements of web slitting apparatus, comprising a'pair of carrier members one of which is adapted to carry a slitter knife and the other of which is adapted to carry 'a counter-member against which said knife can cut a web moved along a path extending between the knife and the counter-member and between confronting faces of said carrier members, in which said faces are of complementary forms such that whenever said carrier members are urged together said faces interengage with one another to oppose relative movement between said carrier members across said path while permitting relative movement between said carrier members and any web engaged therebetween.

It will be understood that whenever the said confronting faces are urged together, any web passing therebetween will be temporarily deformed; it is preferred that said faces are so formed that this tempoary deformation of the web is of the nature of one or more longitudinal corrugations, i.e. that one of said faces has one or more elongated projections extending parallel to the path of the web and the other of said faces has a complementary recess or recesses. If the web is of sufiiciently high strength and has low frictional drag on the material of the said faces, then the latter may be polished integral surfaces of the carrier members. Preferably however each elongated projection on the one face comprises a roller freely rotatable about an axis parallel to the path of the'web, the or each recess in the other face being defined by a pair of such rollers with their axes similarly orientated; in a particularly preferred arrangement the one face has two projectionseach in the form of such a roller, and the other face has two recesses each thus defined by a pair of rollers. In yet another arrangement, one face has projections in the form of single rotatable balls, hile the other face has recesses defined by groups of rotatable balls. Such groups may each, for example, comprise three balls in triangular disposition so as to locate an associated single ball on the one face both laterally and longitudinally.

If the carrier members, while interengaged, are moved from a position clear of the web across the edge of the web, damage to the web could result. This may be avoided by arranging for one of the carrier members to tilt as it crosses the edge of the web, but it is preferred to provide tapes between the interengaging parts of the carrier members. In one form, two stationary tapes may be stretched across the path of the web, one above and one below said path, so that the web is not directly engaged by the carrier member but is held between the tapes when the carrier members are interengaged. Alternatively, where the carrier members have elongated projections in the form of rollers, an endless tape may be provided around the rollers of each carrier member (additional idler rollers being provided as necessary), the interengagement of the rollers causing the two tapes to form a lap through which the web passes when the carrier members move across theweb.

Preferably also power means is provided for moving the carrier member across the web path; by virtue of the interengagement of the confronting faces of the carrier members when the latter are urged together, the power means need be associated with only one of said carrier members. At least one of the carrier members may advantageously be supported upon wheels engaged with a track extending transversely of the web path. One of the carrier members may carry a motor for driving the knife or counter-member; preferably however, a common drive is providedfor all the counter-members by arranging a driven roller, preferably faced with rubber or similar material, to extend across the web path in frictional engagement with all the counter-members.

-It is generally desirable to suspend the slitting operation when the position of the cutter elements is being changed and therefore the carrier members are preferably arranged to carry the knife and counter-member in such manner as to permit separation of the cutter elements at such times; for this purpose preferably either the knife or the counter-member is movably mounted on its associated carrier member, although both the cutting elements may be so mounted if desired.

The scope of the invention extends also to web slitting apparatus including one or more carriers as set out above. Where two or more carriers are provided in apparatus embodying the invention, it is preferred to provide a common support member in the form of a beam or the like extending across the apparatus, through which common support member one of the carrier members of each carrier is supported. This arrangement permits the carrier members of all the carriers to be urged together (and separated) simultaneously before (and after) change of their positions across the web path. Such a common support member may conveniently be associated with the upper carrier members while the lower carrier members are supported on wheels engaged with a common track, the common support member and common track both extending transversely of the web path, above and below it respectively.

In another form of carrier embodying the invention, one of the confronting faces may have one or more elongated projections each in the form of a perforated air pipe, the other face having one or more recesses each defined by a pair of such pipes, means being provided to supply compressed air to all said pipes when the confronting faces of the carrier members are interengaged so that air is blown out of the perforations of the pipes to provide air bearings between the confronting faces and any web lying therebetween.

In order that the invention may be well understood, a preferred embodiment thereof will now be described in more detail, reference being made to the accompanying drawings in which:

FIG. 1 is a view of a web slitting apparatus embodying the invention as seen from the side, i.e. looking across the web path;

FIG. 2 is a view on a larger scale of part of the apparatus of FIG. 1 as seen from the end, i.e. looking along the web path; and

FIGS. 3, 4, and 6 are diagrammatic detail views showing the significant parts of modified forms of carrier member.

Referring first to FIG. 1, a supporting base structure generally indicated at 1 includes guides 2, 3 over which a paper web 4 travels in the direction indicated by arrow 5. After passing over the guide 2 at the upstream side of the apparatus, the web 4 passes between one or more pairs of cutting elements, each such pair comprising a rotatable knife 6 and a motor-driven rotary counter-member 7 respectively positioned above and below the path of the web 4. (It will be understood that while only one such pair of cutting elements is seen in FIG. 1, any other such pairs of elements are disposed at different positions across the web 4, i.e. in front of or behind the plane of FIG. 1). The counter-member 7 is carried on a shaft 8 supported in brackets 9 fixedly secured to a lower carrier member 10, while the knife 6 is carried on a shaft 11 supported in swingable arms 12 i on brackets 13 fixed .to an upper carrier'member 14.

The lower carrier member 10 is supported on rollers 15 running on a track comprising a base 16 and side guides 17; the upper carrier member 14 is suspended from an inverted channel-section beam 18, said member 14 having wheels 19 running upon ribs 20 formed in the vertical internal surfaces of the beam 18. The beam 18 is located above the track 16, 17 and both extend across the apparatus at right-angles to the path of the paper web 4.

The confronting faces of the carrier members, i.e. the bottom face of the .upper carrier member 14 and the top face of the lower carrier member 10, are formed so as to interengage in a manner preventing relative movement across the web between said carrier members when they are urged together. This is achieved by providing the bottom face of the upper carrier member 14 with two rollers 21 and the top face of the lower carrier member 10 with two pairs of rollers 22, so arranged that when the two carrier members are urged together, each roller 21 enters a recess 23 defined by one of the pairs of rollers 22. All the rollers 21, 22 are mounted so as to be freely rotatable about axes parallel to the path of the web 4.

While the apparatus is operating to slit the web 4, the upper carrier member 14 is raised so that the rollers 21 are out of contact with the web 4. The normal path of the web is moreover slightly above the rollers 22. The upper carrier member 14 is lowered to the position shown in FIGS. 1 and 2 only when the position of the cutting elements transversely of the web is to be changed; with said upper carrier lowered, so that the rollers 21, 22 interengage as best seen in FIG. 2, either one of the carrier members l0, 14 may be urged horizontally across the path of the web, and the interengagement of the rollers will cause the other carrier member to move also so that the two carrier members (and hence cutting elements 6, 7) remain in the same relative positions one above the other. Most conveniently, the power devices for moving the carrier members are associated with the lower carrier members. During any such transverse movement of the carrier members, the cutting elements are rendered inoperative by raising the knife 6.

Raising and lowering movements of the upper carrier members are effected by pneumatic rams 24 upon which the beam 18 is hung from an upper frame member 25.

In web slitting apparatus it is common practice to provide a splitter plate downstream of each pair of cutting elements, said splitter plate serving to hold apart the adjacent parts of the web which have just been separated by the cutting elements. Each of the upper carrier members of the present apparatus is provided with a vertically-slidable splitter-plate 26, this plate being resiliently biased by a spring (not shown) to an upper position within the upper carrier member 14. When slitting of the web is to commence, the knife 6 is lowered, the beam 18 is raised to lift the upper carrier members clear of the web 4, and the splitter plates 26 are lowered to protrude below the plane of the web 4 (FIG. 1). The lowering of the plates 26 is effected by hydraulic rams 27, one of which is shown in FIG. 2, mounted on the beam 18 and connected to a pusher bar 28 extending horizontally within saidbeam and parallel thereto. Each splitter plate 26 has an upward extension 29 which projects above the associated upper carrier member 14 for engagement by the pusher bar 28. i

The number of carriers for cutting elements provided will of course be determined by the maximum number of longitudinal cuts required to be made at any one time. When less than this maximum number of cuts is to be made, one or more of the pairs of cutting elements will not be required to be operative and desirably therefore provision is made for moving carriers clear of the path of the web at one or both sides. As seen in FIG. 2, the beam 18 therefore extends beyond the edges of the web 4, and carriers may be moved clear of the web as required. When, however, a carrier is to be moved in the opposite sense, from a position clear of the web to a position within the width of the web, this is done with the two carrier members held together, i.e. with the beam 18 lowered, and the web 4 therefore has to be introduced between the interengaged rollers 21, 22. To effect this without damage to the edge of the web 4, each carrier is caused to tilt as it is moved past the edge of the web, as illustrated at the left of FIG. 2. The vertical faces of the upper carrier member 14 adjacent to the vertical internal surfaces of the beam 18 are provided with cam grooves 30 and the beam 18 carries follower pins 31 on its opposed internal surfaces, below the ribs 20. The positioning of the pins 31 along the length of the beam 18 is such that as a carrier which has been positioned clear of the web is moved towards the edge of the web, the grooves 30 of that carrier embrace the pins 31 shortly before the leading roller 21 of the upper carrier member 14 encounters the edge of the web 4; the form of the grooves 30 is such that the upper carrier member 14 is caused to tilt, lifting the leading roller 21 as the latter meets the edge of the web, and then the member 14 is returned to its normal attitude when the leading roller 21 has passed over said edge. As the trailing roller 21 approaches the edge of the web, this is also lifted to clear said edge, the member 14 tilting again due to cam action between the pins 31 and grooves 30. Each time that the member 14 is thus tilted, while one of the rollers 21 is lifted clear of its associated pair of rollers 22 the other roller 21 remains engaged between its pair of rollers 22 so that the upper and lower carrier members14, continue to move in unison.

While the counter-members 7 may be driven by individual motors in known manner, as economic and efficient common drive may be provided by providing a driving roller 32, indicated in dashed lines in FIG. 1, extending across the path of the web adjacent to the counter members 7 and in frictional engagement with all said counter-members. It will be apparent that this arrangement requires only a single driving motor (not shown) coupled to the roller 32, and also permits the counter-members to be moved to new positions without interruption of their drives, although no air-lines, electric cables or other power transmission devices need be coupled to the carrier members as is necessary when the counter-members (or knives) have individual motors also carried upon the carrier members.

When the carriers are to be moved across the web as described above, while this may notionally be effected manually it is in practice desirable to. provide some form of powered driving device; it is not relevant to the present invention what form of powered driving device is provided for this purpose; for example, each lower carrier member may have an associated hydraulic or pneumatic ram, or a common drive may be engageable with each lower carrier member as required.

The apparatus illustrated in FIGS. 1 and 2 may be simplified and improved in certain respects. As shown, the web 4 is slit by the cutting elements before it passes between the carrier members 10, 14 and this has two consequences firstly, the slitter plate 26 is necessarily in the vicinity of the carrier members and secondly, dust created by the slitting of the web travels towards the carrier members 10, 14 where its presence is undesirable. Accordingly therefore it is advantageous to arrange the apparatus so that the web travels in the opposite direction from that shown, i.e. it travels from left to right as seen in FIG. 1. Slitter dust is then carried away from the members 10, 14 and no splitter plate need (or can) be provided in the vicinity of the carrier members. To separate the parts of the web after slitting, slitter plates may be provided to the right (as seen in FIG. 1) of the cutting elements or, preferably, a separating device of the kind known in the art as a set of Mount Hope rollers may be provided in this region. This latter device comprises a plurality of short freelyrotatable rollers carried by an arcuate support shaft extending transversely of the web, said rollers engaging the slit web so that the latter is curved to an arcuate form (when viewed along its length) thus separating the several parts into which it has been divided by the cutting elements.

The apparatus described above with reference to FIGS. 1 and 2 can also with advantage be improved by elimination of the cam grooves 30 and coacting pins 31. The need for tilting the carrier members as they move across the edge of the web can be avoided by providing tapes adjacent to each face of the web and two modified forms of apparatus embodying such tapes are shown diagrammatically in FIGS. 3 and 4. Referring first to FIG. 3, in this form two tapes 40, 41 are stretched across the path of the web 4 and lie very close to the web, respectively just above and just below said web. The ends of the tapes 40, 41 are secured through respective tension springs 42, 43 to convenient parts of the apparatus indicated at 44, 45. The rollers 21, 22 of the carrier members 14, 10 thus engage one another through the top tapes 40, 41 and the web 4 lying between said tapes and it will be apparent that there is no need for any tilting of either carrier member as the rollers 21, 22 move across the edge of the web 4.

It will be understood that the tapes 40, 41 are desirably moved apart whenever the carrier members are separated and web slitting commences, and this is readily effected by arranging that the parts 44 are connected to the beam 18.

The second modified form of apparatus illustrated in FIG. 4 employs endless tapes. In this form, the upper carrier member (not shown in FIG. 4) not only carries roller 21, butalso carries two idler rollers 50, 51 placed symmetrically above and to either side of the roller 21. An endless tape 52 is fitted around the three rollers 21, 50, 51. The lower carrier member (also not shown in FIG.'4) carries not only the rollers 22, but also a single idler roller 53 placed symmetrically below and between the two rollers 22. An endless tape 54 is fitted around the three rollers 22, 53, 22. The interengagement of the rollers 21, 22 when the two 'carrier members are brought together as shown produces a lap between the tapes 52, 54 and it will readily be appreciated that this permits the carrier members to be moved on to the web 4, across its edge, without need for tilting the upper carrier member as previously described.

Turning now to FIG. 5, this illustrates a further modified form of apparatus in which no rollers are provided on the carrier members. In their place we provide perforated air pipes 60, 61. The pipe is fitted 'to the upper carrier member (not shown in FIG. 5) in place of roller 21 and has two rows of perforations 62 directed downwardly and to each side i.e. towards the pipes 61 which are provided on the lower carrier member (not shown in FIG. 5) in place of rollers 22. Each of the pipes 61 has a single row of perforations 63 directed upwardly and inwardly i.e. towards the pipe 60. (The rows of perforations 61, 63 include further perforations in front of and behind'the plane of the drawings).

With this form of apparatus whenever the carrier members are interengaged for movement across the web 4, compressed air is fed to the pipes 60, 61, 61 and streams of air therefore emerge from the perforations 62, 63 towards the upper and lower faces of the web 4 respectively. This establishes a so-called air bearing" between the pipes 61 and the pipe 60, so that when the lower carrier member is moved transversely of the web 4 the upper carrier member is also moved by thrust transmitted through the air bearing. This arrangement of course does not involve any contact between any parts of the carrier members and the web as the carrier members are moved and this avoids marking of the web or other damage. When tapes are used, as shown in FIG. 3 or FIG. 4, there is no need for tilting of the upper carrier member. The use of such an air bearing allows the carrier members to be moved when the web 4 is in motion.

It may be noted that, while in FIG. 2 and in FIG. 3 there are shown two sets of rollers 21, 22 for each pair of carrier members, it is possible in many instances for one set of rollers to be sufficient. With one set of rollers, the whole force to be transmitted to move the upper carrier member across the web is applied through this one set of rollers and this may be excessive, especially where the rollers directly engage the web and the web is of a mechanically weak material. However, with a strong web and/or when tapes are fitted, a single set-of rollers 21, 22 may be permissible. In another embodiment, illustrated in FIG. 6, the arrangement of rollers on the respective faces may be replaced by rotatable balls provided on the respective faces of the carrier members. In such an arrangement, one face of a carrier has projections in the form of single rotatable balls 70, while face of the othe'r carrier has recesses defined by groups of rotatable balls 72.

What we claim as our invention and desire, to secure by Letters Patent is:

1. A carrier for cutting elements of web slitting apparatus, comprising a pair of carrier members one of which is adapted to carry a slitter knife and the other of which is adapted to carry a counter-member against which said knife can cut a web moved along a path extending between the knife and the counter-member and between confronting faces of said carrier members, in which said faces are of complementary forms such that whenever said carrier members are urged together.

said faces interengage with one another to oppose relative movement between said carrier, members across said path while permitting relative movement between said carrier members and any web engaged therebetween.

2. A carrier as claimed in claim 1 in which one of said faces has one or more elongated projections extending parallel to the path of the web and the other of said faces has a complementary recess or recesses.

3. A carrier as claimed in claim 2, in which each elongated projection on the one face comprises a roller freely rotatable about an axis parallel to the path of the web, each recess in the other face being defined by a pair of such rollers with their axes similarly orientated.

4. A carrier as claimed in claim 3, including an endless tape passing around the roller on the one face, said tape being further supported by a pair of idler rollers carried by the same carrier member, and a further endless tape passing around both rollers of the pair, the latter tape being further supported by an idler roller carried by the same carrier member as the pair of rollers, so that interengagement between the roller on the one face and the pair of rollers on the other face can only take place through the two tapes and any web lying there-between.

5. A carrier as claimed in claim 3, including two stationary tapes stretched across the path of the web, one above and one below said path, so that when the confronting faces are interengaged any web lying therebetween is not directly engaged by the carrier members but is held between said tapes.

6. A carrier as claimed in claim 2, in which each of said elongated projections comprises a perforated air pipe and each of said recesses is defined by a pair of such pipes, means being provided to supply compressed air to all said pipes when the confronting faces are interengaged so that air is blown out of the perforations of the pipes to provide air bearings between the confronting faces and any web lying therebetween.

7. A carrier as claimed in claim 6, in which at least one of the carrier members is supported upon wheels engaged with a track extending transversely of the web path.

8. A carrier as claimed in claim 7, including means for urging said carrier members together and for separating said carrier members before and after change of their positions across the web path, and means for respectively separating and bringing together the knife and the counter-member, so that the latter are in cutting relation when said carrier members are separated and are separated when said carrier members are urged together.

9. A carrier as claimed in claim 1, in which one of said faces has projections in the form of single rotatable balls and the other of said faces has recesses defined by groups of rotatable balls.

10. Web slitting apparatus including a carrier as claimed in claim 1.

11. Apparatus as claimed in claim 10, including a plurality of said carriers and common means for simultaneously urging together and separating the carrier members of all the carriers.

12. A carrier as claimed in claim 1, including two stationary tapes stretched across the path of the web, one above and one below said path, so that when the confronting faces are interengaged any web lying therebetween is not directly engaged by the carrier members but is held between said tapes.

13. A carrier as claimed in claim 1, in which at least one of the carrier members is supported upon wheels engaged with a track extending transversely of the web path.

14. A carrier as claimed in claim 1, including means for urging said carrier members together and for separating said carrier members before and after change of their positions across the web path, and means for respectively separating and bringing together the knife and the counter-member, so that the latter are in cutting relation when said carrier members are separated and are separated when said carrier members are urged together. 

1. A carrier for cutting elements of web slitting apparatus, comprising a pair of carrier members one of which is adapted to carry a Slitter knife and the other of which is adapted to carry a counter-member against which said knife can cut a web moved along a path extending between the knife and the counter-member and between confronting faces of said carrier members, in which said faces are of complementary forms such that whenever said carrier members are urged together said faces interengage with one another to oppose relative movement between said carrier members across said path while permitting relative movement between said carrier members and any web engaged therebetween.
 2. A carrier as claimed in claim 1 in which one of said faces has one or more elongated projections extending parallel to the path of the web and the other of said faces has a complementary recess or recesses.
 3. A carrier as claimed in claim 2, in which each elongated projection on the one face comprises a roller freely rotatable about an axis parallel to the path of the web, each recess in the other face being defined by a pair of such rollers with their axes similarly orientated.
 4. A carrier as claimed in claim 3, including an endless tape passing around the roller on the one face, said tape being further supported by a pair of idler rollers carried by the same carrier member, and a further endless tape passing around both rollers of the pair, the latter tape being further supported by an idler roller carried by the same carrier member as the pair of rollers, so that interengagement between the roller on the one face and the pair of rollers on the other face can only take place through the two tapes and any web lying there-between.
 5. A carrier as claimed in claim 3, including two stationary tapes stretched across the path of the web, one above and one below said path, so that when the confronting faces are interengaged any web lying therebetween is not directly engaged by the carrier members but is held between said tapes.
 6. A carrier as claimed in claim 2, in which each of said elongated projections comprises a perforated air pipe and each of said recesses is defined by a pair of such pipes, means being provided to supply compressed air to all said pipes when the confronting faces are interengaged so that air is blown out of the perforations of the pipes to provide air bearings between the confronting faces and any web lying therebetween.
 7. A carrier as claimed in claim 6, in which at least one of the carrier members is supported upon wheels engaged with a track extending transversely of the web path.
 8. A carrier as claimed in claim 7, including means for urging said carrier members together and for separating said carrier members before and after change of their positions across the web path, and means for respectively separating and bringing together the knife and the counter-member, so that the latter are in cutting relation when said carrier members are separated and are separated when said carrier members are urged together.
 9. A carrier as claimed in claim 1, in which one of said faces has projections in the form of single rotatable balls and the other of said faces has recesses defined by groups of rotatable balls.
 10. Web slitting apparatus including a carrier as claimed in claim
 1. 11. Apparatus as claimed in claim 10, including a plurality of said carriers and common means for simultaneously urging together and separating the carrier members of all the carriers.
 12. A carrier as claimed in claim 1, including two stationary tapes stretched across the path of the web, one above and one below said path, so that when the confronting faces are interengaged any web lying therebetween is not directly engaged by the carrier members but is held between said tapes.
 13. A carrier as claimed in claim 1, in which at least one of the carrier members is supported upon wheels engaged with a track extending transversely of the web path.
 14. A carrier as claimed in claim 1, including means for urging said carrier members together and for separating said carrier members before and after chanGe of their positions across the web path, and means for respectively separating and bringing together the knife and the counter-member, so that the latter are in cutting relation when said carrier members are separated and are separated when said carrier members are urged together. 